chore: allow DNS queries from Uncloud containers to the embedded DNS server

internal/machine/firewall/iptables_darwin.go

@@ -0,0 +1,8 @@
+package firewall
+
+import "fmt"
+
+// ConfigureIptablesChains is a stub for Darwin.
+func ConfigureIptablesChains() error {
+	return fmt.Errorf("not supported on Darwin")
+}